Attack bane Eirika worth using?

I would absolutely still use her. That low attack stat will be hard to swallow, but when you consider how amazingly she will work with Nino, I think it will be fine.

The speed and attack buffs she gives will also help your other team members, and between the high attack potential of Sharena, Lucina and Nino, you should have plenty of damage. The only drawback is that you would lose that extra move from Olivia, which could mess up your play style. But overall, I think she would still work very well.

I kind of know where you're coming from; My team consist of Julia, Sharena, Olivia, and Nino.